What are the 'known' ports?

In Internet networking, the IANA Port Number Registry divides the 16-bit TCP/UDP port field into three ranges. The “Well-Known Ports” range, historically called the “known ports,” spans 0–1023 and is reserved for the most ubiquitous services (e.g., HTTP 80, HTTPS 443, SSH 22). These numbers are assigned and controlled by IANA so that client software can predictably contact standard services on remote hosts.

A. Lists two well-known ports and one dynamic port (65431); not a defined range.

C. 49152–65535 are the Dynamic/Private ports allocated ephemerally by clients, not “known” ports.

D. 1024–49151 constitute the Registered ports range, assigned to specific applications but not universally “known.”

1. RFC 6335

“IANA Procedures for the Management of the Service Name and Transport Protocol Port Number Registry

” Sec. 6

pp. 7–8.

2. IANA

“Service Name and Transport Protocol Port Number Registry – Introduction

” ¶2 (2023-10-30).

3. Comer

D. E. “Internetworking with TCP/IP

Vol. 1

” 6th ed.

Chap. 23

pp. 408–409 (Pearson

2014).

4. MIT OpenCourseWare

6.033 “Computer Systems Engineering

” Lecture 9 notes

slide 12 (Port Number Ranges).